This invention relates to the construction of pneumatic tires and especially to the forming of superposed carcass plys, sidewall strips and an extruded tread strip into a laminated band that is subsequently shaped and vulcanized to form a pneumatic tire. More particularly, the invention relates to a novel means for forming the tread portion of the tire to provide improved balance.
In the construction of pneumatic tires, particularly tires of larger bead radius, an imbalance frequently occurs due to the extra weight in the zone of the tread splice. The imbalance is either due to the splicing operation during assembly of the tire and/or free shrinkage of the cut-to-length tread strip near the free ends after cutting. Normally an extruded, cut-to-length strip of uncured tread rubber is wrapped around the tire carcass during fabrication, usually over one or more breaker strips, and then lap spliced at its ends. The extra weight in the area of the tread splice creates an imbalance in the finished tire or stated another way causes the center of mass of the tire to be disadvantageously spaced from the geometric axis of the tire.
This problem becomes more significant in tires of larger size such as passenger car tires of sizes "G" and above.
The method and apparatus of the present invention, however, improve the balance of the tire by counterbalancing the extra weight in the zone of the tread strip splice, and afford other features and advantages heretofore not obtainable.